It is most likely that the polypropylene rope, used to snug the top of the bonnet, slid up the beckets and the bonnet opened in flight. The pilot described seeing the starboard front area of the bonnet folded in, likely because the separated becket allowed the formation of an asymmetric shape. The resulting shape and the bonnet's light weight and high drag allowed the bonnet to fly up and into the flight path of the helicopter, carrying the longline with it. The longline subsequently came into contact with the tail rotor and disabled it, rendering the helicopter uncontrollable. At impact, it is likely that the pilot's upper body moved around the cabin. This would have been facilitated by the lack of an upper-body restraining device and is evident by the pilot's fractured helmet. The helmet protected the pilot's head from severe injury, thereby allowing him to extricate himself from the sunken wreckage. However, in this particular helicopter, even when persons occupying either front seat are properly secured, they risk hitting their heads on the fixture to which the liferaft is normally secured. The colour of the pilot's helmet and flight suit (grey and navy blue, respectively) made it difficult to see him in the ocean, thereby increasing the risk of him not being found and rescued.Analysis It is most likely that the polypropylene rope, used to snug the top of the bonnet, slid up the beckets and the bonnet opened in flight. The pilot described seeing the starboard front area of the bonnet folded in, likely because the separated becket allowed the formation of an asymmetric shape. The resulting shape and the bonnet's light weight and high drag allowed the bonnet to fly up and into the flight path of the helicopter, carrying the longline with it. The longline subsequently came into contact with the tail rotor and disabled it, rendering the helicopter uncontrollable. At impact, it is likely that the pilot's upper body moved around the cabin. This would have been facilitated by the lack of an upper-body restraining device and is evident by the pilot's fractured helmet. The helmet protected the pilot's head from severe injury, thereby allowing him to extricate himself from the sunken wreckage. However, in this particular helicopter, even when persons occupying either front seat are properly secured, they risk hitting their heads on the fixture to which the liferaft is normally secured. The colour of the pilot's helmet and flight suit (grey and navy blue, respectively) made it difficult to see him in the ocean, thereby increasing the risk of him not being found and rescued. The rope used to snug the top of the bonnet most likely slid up the beckets, allowing the bonnet to open and fly into the flight path of the helicopter carrying the longline with it. The longline came into contact with the tail rotor and disabled it, rendering the helicopter uncontrollable.Finding as to Causes and Contributing Factors The rope used to snug the top of the bonnet most likely slid up the beckets, allowing the bonnet to open and fly into the flight path of the helicopter carrying the longline with it. The longline came into contact with the tail rotor and disabled it, rendering the helicopter uncontrollable. Most helicopters are not designed or certified to accommodate vertical reference external load operations; however, these operations are very common and pilots fly in this higher-risk environment without proper safety-restraint devices. It is likely that the pilot's unrestrained upper body moved around the cabin at impact. This increased the risk of injury and, in this case, the risk of drowning. Even when properly secured, persons in either front seat risk hitting their heads on a fixture to which the liferaft is normally secured. The colour of the pilot's helmet, life-vest cover and flight suit (grey and navy blue, respectively) made it difficult to see him in the ocean, increasing the risk of him not being found and rescued.Findings as to Risk Most helicopters are not designed or certified to accommodate vertical reference external load operations; however, these operations are very common and pilots fly in this higher-risk environment without proper safety-restraint devices. It is likely that the pilot's unrestrained upper body moved around the cabin at impact. This increased the risk of injury and, in this case, the risk of drowning. Even when properly secured, persons in either front seat risk hitting their heads on a fixture to which the liferaft is normally secured. The colour of the pilot's helmet, life-vest cover and flight suit (grey and navy blue, respectively) made it difficult to see him in the ocean, increasing the risk of him not being found and rescued. The pilot's helmet protected his head from severe injury, allowing him to extricate himself from the sunken wreckage.Other Finding The pilot's helmet protected his head from severe injury, allowing him to extricate himself from the sunken wreckage. Safety Action Transport Canada On 09 May 2005, Transport Canada Aircraft Services Directorate issued a safety notice, restricting operations with empty or light external sling loads. On 25 May 2005, Transport Canada Aircraft Services Directorate produced draft Standard Operating Procedures (SOPs) for helicopter external load operations. These SOPs restrict the use of bonnets and caution pilots about light and unstable loads. Transportation Safety Board On 31 May 2005, the TSB Director of Investigations (Air) sent a Safety Information Letter to Transport Canada, outlining the facts of this accident that showed that, despite the Canadian Aviation Regulations (CARs) and the previous Safety Advisory to Transport Canada (A010006), helicopter slinging operations without upper-body restraint continue. In response to the above-noted letter, Transport Canada provided the following: If the upper-body restraint equipment is used properly, and in accordance with the CARs, they will provide the protection intended by those requirements. It is the operations being conducted when these accidents occurred that led the pilots to loosen and/or remove elements of their restraint system. The existing CARs (Section 605.27(3)) require at least one pilot to have the safety belt, which as per the definition in Section 101.01 of the CARs, includes the shoulder harness fastened during flight time. If an operator discovers that installed equipment, shoulder harness in this case, is unsuitable for Vertical Reference Helicopter Sling Operations then Transport Canada has a well-established process in place for assessing and approving supplemental aircraft equipment. It is the responsibility of the industry to comply with the regulations, and, if warranted, apply for an approval of a configuration to meet the industry's operational needs. Transport Canada continues to welcome air operator and manufacturer initiatives to promote safe helicopter external load operations. Notwithstanding the current regulations and industry initiatives undertaken to date, Transport Canada has initiated the process to conduct research and development on the issue. A proposal has been submitted to the Civil Aviation Research and Development Committee to study crew restraint in vertical reference external load (VREL) operations. The objective is to develop a new restraint system and produce a safety education and promotion product on VREL operations. On 31 May 2005, the TSB Director of Investigations (Air) sent a safety advisory to Transport Canada, indicating that, during this investigation, a test revealed that, even when properly restrained, persons seated in either of the front seats are able to hit their heads on a fixture installed to hold a liferaft. The advisory suggested that Transport Canada may wish to modify the fixtures that hold the liferafts in the Messerschmitt-Bolkow-Blohm BO105 helicopters to remove the hazard or limit use of the front seats to persons wearing protective head gear. It also suggested that Transport Canada may wish to verify that other aircraft have not been modified to induce similar hazards. In response to the above-noted safety advisory, Transport Canada provided the following: Transport Canada is undertaking a complete review of the applicable Limited Supplemental Type Certificate (LSTC) data package with regards to this occurrence. The data used to show compliance with Section27.561 of the United States Federal Aviation Regulations are being reviewed and a determination will be made as to whether a design change is required. Although the review is not yet complete, it is possible that padding could be added to the fixture and a requirement be made that helmets are to be worn with this installation. On 01 June 2005, the TSB Director of Investigations (Air) sent a safety information letter to Transport Canada, highlighting the facts of this accident and the continued operational practices of helicopters carrying empty or light slings. The letter pointed out that the Board had made a recommendation (A93-12) to Transport Canada in 1993that it coordinate the development and implementation of airworthiness standards and operational limitations for helicopter slinging equipment. In response to the above-noted safety information letter, Transport Canada provided the following: Chapter 527.865 of the CARs addresses external loads for normal category helicopters and Chapter529.865 of the CARs deals with transport category helicopters. These standards state the certification basis for helicopters equipped with external slinging capabilities (cargo hook). Helicopter slinging equipment is considered part of the load rather than the helicopter; therefore, it is not subjected to a Technical Standard Order (TSO) or STC approval process. The responsibility to ensure safe slinging operations remains with the operator, and specific information on slinging and crew training is to be contained in the company operations manual. Transport Canada continues to welcome air operator and manufacturer initiatives to promote safe helicopter external load operations. Strategies to address helicopter rotor/sling strikes, and unsafe equipment and practices that lead to them, have included numerous articles in Transport Canada's safety publications such as the Aviation Safety Vortex newsletter. Transport Canada continues to be concerned with this area of operations. Currently, the Department is producing a new safety awareness video titled Helicopter External Load Operations, Ground Crew Safety. The video's intended audience is ground crew operations and will address subjects such as occupational safety and health issues, briefings, protective equipment, communications and checking load and equipment such as straps and bonnets. Transport Canada is drafting another article based on this information letter for publication in Transport Canada's Aviation Safety Letter.